HATCHERY REQUIREMENTS 25 



microbial breakdown of waste feed, most of it comes from fish metabolism. 

 The amount of metabolism, hence the amount of ammonia excreted, is 

 conditioned by the amount of food fish eat. For each hatchery and feed 

 type, an ammonia factor can be calculated: 



ppm total ammonia x ,^p m water inflow 



ammonia factor = — - — , . , ; 



lbs food ted per day 



Here, ppm is parts per million concentration, gpm is gallons per minute 

 flow, and lbs is pounds. To establish the ammonia factor, total ammonia 

 should be measured in raceways, tanks, and ponds several times over one 

 day. Once the factor is established, the formula can be turned around to 

 give estimates of total ammonia: 



lbs food/day x ammonia factor 



ppm total ammonia = ~ 



gpm flow 



Then, by reference to Appendix B with the appropriate temperature and 

 pH, the concentration of un-ionized ammonia can be estimated. 



Example: Three raceways in a series have a water flow of 200 gallons 

 per minute. Fish in the first raceway receive 10 pounds of food per day, 5 

 pounds of feed per day go into the second raceway, and 20 pounds of feed 

 per day go into the third. The ammonia factor for these raceways is 3.0. In 

 the absence of any water treatment, what is the expected concentration of 

 total ammonia nitrogen at the bottom of each raceway? 



Raceway 1: = 0.15 ppm 



^ 200 



^ (10+5)X3 ^^„ 



Raceway 2: = 0.23 ppm 



^ 200 



^ _ (10 + 5 + 20) X 3 



Raceway 3: = 0.53 ppm 



^ 200 ^ 



Treatment of Effluent Water and Sludge 



The potential of hatchery effluent for polluting streams is very great. Like 

 any other source of waste water, hatcheries are subject to federal, state, and 

 local regulations regarding pollution. The United States Environmental 

 Protection Agency requires permits of hatcheries that discharge effluent 

 into navigable streams or their tributaries. Hatchery operators are responsi- 

 ble for knowing the regulations that apply to their facilities. Some treat- 

 ment of hatchery effluent is required of almost every hatchery. This is true 

 even for systems that recycle and treat water internally; their advantage 



